1. Field of the Invention
The present invention relates to a power supply apparatus which supplies power to a body-insertable apparatus in a subject from outside the subject. The body-insertable apparatus is exemplified by a swallowable capsule endoscope.
2. Description of the Related Art
In recent years, a capsule endoscope equipped with an imaging function and a radio function has appeared in the endoscope field. The capsule endoscope is moved in internal organs such as a stomach and a small intestine (or in body cavities) with peristaltic motion thereof to sequentially perform imaging in the body cavities using the imaging function in an observation period during which the capsule endoscope is swallowed into a subject as a tested body for observation (examination) and is naturally discharged from the living body as the subject.
Image data imaged in the body cavities by the capsule endoscope in the observation period of movement in these internal organs is sequentially transmitted to an external device provided outside the subject by the radio function such as radio communication and is then stored in a memory provided in the external device. The subject carries the external device having the radio function and the memory function. The subject can be freely moved in the observation period during which the capsule endoscope is swallowed and discharged. After observation, a doctor or a nurse can display the images in the body cavities on a display device such as a display based on the image data stored in the memory of the external device to perform diagnosis.
JP-A No. 2001-231186 (KOKAI) (page 3, FIG. 1) shows one conventional system for supplying power to the capsule endoscope of the above-described type. When a radio capsule (corresponding to the capsule endoscope) is placed inside the living subject, the system transmits the power from outside the subject to an inside of the capsule endoscope. The system includes an external device having a power-transmitting antenna and the capsule endoscope having a power-receiving antenna arranged therein. The external device supplies power to the capsule endoscope through the power-transmitting antenna and the power-receiving antenna, whereby the capsule endoscope can perform an observation operation in the subject for an extended period of time.